Effects of nutrient addition on foliar phosphorus fractions and their resorption in different-aged leaves of Chinese fir in subtropical China.

Background and aims: Anthropogenic activities have increased nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which may significantly alter P cycle through accumulation and resorption. Methods: We measured the concentrations of four different P fractions (inorganic, nucleic, sugar, and residual P) in both live leaves and senescent leaves in N and P additions in an evergreen plantation forest of subtropical China. Results: Adding moderate N plus P increased total, inorganic, and sugar P concentrations, which sustained the leaf N/P balance and alleviated P limitation in Chinese fir (Cunninghamia lanceolata) plantation. Nitrogen and P (total, nucleic, and residue P) resorption proficiencies did but P (each of various fractions) resorption efficiency did not respond to nutrient addition. The concentrations and resorption efficiencies of most P fractions were lower in the old than young leaves, but their resorption proficiencies except for sugar P weren't different. Conclusions: Internal P cycles of Chinese fir could be strongly altered through increasing accumulation of inorganic P and sugar P factions in respond to soil P enrichment when combined with suitable N addition. The easily degradable P (inorganic and sugar P) were preferentially resorbed regardless of nutrient addition. Leaf age was a key-factor influencing the resorption extent of P fractions in Chinese fir. [ABSTRACT FROM AUTHOR]